Question

is required to accept electron 17. At the very end of the electron transport chain in the mitochondria, final electron acceptor. A. carbon dioxide B. ADP C. ATP Synthase Doxygen E. NAD+ 18. Select the correct flow of energy transfer during cellular respiration. A. NADHH gradient glucose → ATP B glucose → NADH H gradient ATP C. glucose H gradient → NADH ATP D. glucose ATPH gradient → NADH 19. If a muscle cell has low levels of oxygen, which of the following will likely occur at higher levels than w are high levels of oxygen? A. citric acid cycle Bylactic acid fermentation C. breakdown of pyruvate D. oxidative phosphorylation 20. In addition to glycolysis, alcohol fermentation and lactic acid fermentation include additional steps that A. create oxygen B, regenerate FADH C. reduce NAD to NADH D. oxidize NADH to NAD E. regenerate ADP 21. During alcohol fermentation, yeast cells y create 2 ATP per glucose as well as CO2 and alcohol B. create 2 ATP per glucose as well as lactic acid C create 4 ATP per glucose as well as CO2 and alcohol D. create more ATP per glucose than cellular respiration E. create 34-38 ATP per glucose 22. The electron transport chain in the mitochondria uses the energy from electrons donated by NADH to A. allow hydrogen ions to diffuse down their gradient B. directly make ATP C. make oxygen D. pump hydrogen ions against their gradient 23. Which of the following is the reactant that provides electrons (electron donor) for the light reactions of photosynthesis? A. oxygen B. NADP C. ATP D. ADP БНО

Answer 1

17. Oxygen is the final electron acceptor in electron transport chain (ETC) during aerobic respiration. Cytochrome c oxidase or complex IV of ETC catalyzes the formation of water from oxygen and protons. ADP binds to pi to form ATP via ATP synthase. ATP synthase uses the chemoosmotic proton gradient from the transfer of electrons through ETC. Carbon dioxide is released after TCA cycle and not in ETC. NAD+ is formed after NADH transfers electrons to complex I of ETC.

Right choice: D. oxygen.

18. In aerobic respiration, glucose enters glycolysis and is converted to two molecules of pyruvate. Pyruvate is converted to acetyl CoA by link reaction. Acetyl CoA enters TCA cycle and CO2, 3NADH2, 1 FADH2 and 1 ATP is formed. NADH2 enters ETC and donates electrons to complex I. This creates protons. Transfer of electrons through the ETC will create protons (H+), which then move to the intermembrane space. As a result a proton gradient is created. H+ are then pumped by F0 unit of ATP synthase into mitochondrial matrix. This movement is used by F1 subunit of ATP synthase to produce ATP from ADP and Pi.

Right choice: B: glucose-> NADH-> H gradient-> ATP

19. Glycolysis form pyruvate from glucose. When oxygen is less, later steps of aerobic respiration are inhibited. Hence, lactate dehydrogenase will convert Pyruvate to lactic acid via anaerobic respiration/fermentation. The lactic acid accumulates and can lead to fatigue. TCA cycle, link reaction (pyruvate to acetyl CoA) and oxidative phosphorylation (ETC) are part of aerobic respiration and require oxygen to function.

Right choice: B. lactic acid fermentation.

20. Alcohol fermentation and lactic acid fermentation are types of anaerobic respiration. There is formation of ethanol and CO2 in alcohol fermentation from pyruvate while lactic acid fermentation forms lactic acid from pyruvate. It is known that glycolysis that produces pyruvate also forms 2NADH. There is no ATP regeneration in lactic acid or alcohol fermentation steps. However, NAD+ is regenerated from NADH, which can then be used for glycolysis. FADH2 is formed in TCA cycle and ADP is regenerated only upon ATP hydrolysis. Oxygen is only formed during photosynthesis in plants.

Right choice: D. oxidize NADH to NAD+

21. In alcohol fermentation, initially glycolysis occurs where glucose breaks down to pyruvate. 2 ATP (4 ATP created but 2 ATP used up) and 2 NADH2 are synthesized per glucose. Pyruvate is first broken down to acetaldehyde and CO2 using the 2 NADH (converted to NAD+). Acetaldehyde then is converted to ethanol. Thus, final products are 2 ATP, ethanol, CO2. Lactic acid is formed from pyruvate during lactic acid fermentation. Fermentation is less efficient process as it produces 2 ATP, while aerobic respiration produces 34-38 ATP (revised to 30-32 ATP).

Right choice: A. create 2 ATP per glucose as well as CO2 and alcohol (ethanol).

22. In the electron transport chain present in inner mitochondrial membrane, NADH will donate 2 electrons to complex I. These electrons pass through complex II-IV and are accepted by oxygen to form water. The energy generated from electrons is used to transport H+ ions from mitochondrial matrix to intermembrane space against their concentration gradient. Four protons are transferred in an active transport mechanism (to intermembrane space) that requires energy. This leads to generation of a chemoosmotic gradient, which is then used by ATP synthase to form ATP. ATP synthase moves protons from intermembrane space to matrix down the concentration gradient.

Right choice: D. pump hydrogen ions against their gradient.

23. In light reaction, photosystem II undergoes excitation of electrons by light energy. These electrons are then transferred via electron carriers to photosystem I to produce ATP. The electrons in photosystem I are also excited by light energy and pass through electron carriers. NADH is produced using ATP, which is then used for dark reactions. ATP hydrolysis produces ADP and Pi. Photolysis of water generates electrons from water, which replenish the electrons lost from photosystem II. Photosystem II replenishes electrons for photosystem I. Oxygen is released during photosynthesis.

Right choice: E. H20